(1) Technical Field
The present disclosure relates to low noise amplifiers (LNAs) and more specifically to programming LNAs for linearity, gain, noise, and current.
(2) Background
Due to increasing use, frequency bands are being added to the mobile wireless spectrum. The number of users has been increasing in many countries and cell phones are made for a global market. The number of frequency bands is increasing and are used in urban and rural environments which presents a challenge on the design of RF front ends for the mobile devices.
One LNA cannot handle the spectrum of frequencies from 0.7 GHz to 3.6 GHz and provide acceptable performance, additionally, LNAs have stringent performance specifications. Since 2.9 GHz is too much bandwidth for one LNA, the spectrum is broken into multiple portions, handled by an LNA.
In the event that one LNA is handling a portion of the spectrum, it is fixed in respect to its performance within that portion of the spectrum. Therefore, if the LNA is used in a cell phone, whether in an urban environment or in a rural environment, its performance is fixed. Difficulties arise from the fact that in an urban environment and a rural environment different demands on the LNA present themselves. In an urban environment with much interference, a high linearity LNA may be optimum and in a rural environment with a possibly weak signal a high gain LNA may be optimum. One LNA cannot provide high linearity and high gain, so typically a compromise is designed in. The instant disclosure provides one possible solution by analyzing the RF signal within a band and switching to an LNA that best meets the incoming signal.